<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>

<body>
  <header>头部</header>
  <section>
    <nav>导航</nav>
    <menu>菜单</menu>
  </section>
  <section>
    <progress max="100" min="0" value="80"></progress>
  </section>

  <footer>脚步</footer>
  <dialog id="mylog">
    <div>你好</div>
    <div>你不好</div>
  </dialog>
  <button id="btn">打开客服</button>
  <button id="close">关闭客服</button>
  <script>
    var mylog = document.getElementById("mylog")
    var btn = document.getElementById("btn")
    var close = document.getElementById("close")
    btn.onclick = function () {
      mylog.setAttribute("open", "open")
    }
    close.onclick = function () {
      mylog.removeAttribute("open")
    }

  </script>
</body>

</html>